The present invention relates to a postage meter and more particularly to a meter setting mechanism for setting print wheels in a postage meter.
Postage meters in use today typically include a set of four adjacent print wheels, each of which carries print characters zero through nine. The print wheels can be independently positioned to allow a user to set any amount of postage between $00.00 (for test purposes) and $99.99.
The print wheels in the type of postage meter in widespread commerical use today are manually set by a user through a series of mechanical linkage and levers. Setting the print wheels manually is no problem for users who process relatively little mail on a daily basis. However, some users process an extremely high volume of mail on a daily basis and need a postage meter with extremely high throughout.
While meter mechanisms in use today can be adapted to more automated operation by using electric motors to drive the linkage and mechanical meter assemblies, such assemblies were not originally designed for operation at high speeds over extended periods of time. The long term mechanical integrity of the linkages and the maximum meter setting speeds attainable are not as high as might be desired. Also, the amount of space required for the linkages and levers has made it difficult to incorporate the slightly-modified mechanical meters into larger systems.
A meter setting mechanism more suited for use in automated systems has been developed. In this system, the print wheels are set by independently-rotatable, adjacent spur gears which are successively meshed with a master gear. The master gear is rotatably-mounted within a yoke which can be shifted along an axis parallel to the common axis of the spur gears. Rotation of the master gear is controlled by a stepping motor. Lateral movement of the yoke is controlled by a pair of solenoids which can be energized individually or simultaneously to rotate pivot arms coupled to the yoke through a toggle pin which serves as a rotary-to-reciprocating motion converter. The pivot arms are spring biased to oppose the actions of the energized solenoids.
While the system just described elminates many of the cumbersome linkages found in prior meter setting mechanisms it is felt that there is still room for improvement. A number of mechanical linkages remain in the described mechanism. Thus, long term reliability problems inherent in mechanical linkages, while greatly reduced are, not completely eliminated. Also, since one or both solenoids are energized at the same time the master gear motor is energized, the power requirements of the meter setting mechanism are higher than desired. Moreover the normal action and reaction of the springs used to bias the solenoids causes vibrations within the system which delay the settling time when the master gear yoke is shifted to new lateral positions.
Finally, the maximum number of yoke positions is limited to four, representing all the possible energization combinations for two dual-position solenoids. Increasing the number of yoke positions to permit more digits to be printed or for security purposes would require development of a new and considerably more complex solenoid mechanism. The use of additional solenoids would, of course, aggravate such problems as settling time and power requirements.
The present system was conceived as an improved meter setting mechanism, that would provide better security and a more positive lock up.